The invention relates to the concentration of ores of non-ferrous metals, and more particularly, to a method for concentrating ores of non-ferrous metals by flotation.
The invention may be most advantageously used in concentrating ores wherein the mineral being concentrated is in finely comminuted form and mineral particles are not completely separated from surrounding rock.
In addition, the invention may be effectively used in the flotation of coal, mineral chemical materials and also for the purification of the effluents.
Several types of flotation methods are used at present for the concentration of ores, and a certain type of ore requires a respective method of flotation.
However, in the majority of applications, none of the existing methods is capable of solving problems of flotation of minerals with a particle size smaller than 10 .mu.m, and particles of ore with a small exposure of mineral grain. In certain constructions the problem of obtaining small-size air bubbles commensurable with the size of particles being flotated is solved, but conditions for effective flotation of minerals are not created.
In the majority of machines, the method of dispersion does not make it possible to obtain air bubbles required for the flotation of fine particles and ore particles with a small exposure of mineral.
Known in the art is a flotation machine (French patent No. 1483994) in which the main parts comprise a nozzle, a bath and a discharge pipeline. The nozzle is so constructed that an air jet is fed to the central zone of a jet, and pulp flows through guide members which impart thereto rotary motion in a circular path.
The nozzle directs the swirled concentric jet of a mixture of pulp and compressed air into a cell. The central air jet is entrained in rotation together with the surrounding pulp. It is the cooperation of pulp and air inside the nozzle that causes the separation of bubbles from the air "core" and ensures good stirring and contact of air bubbles with mineral particles.
The jet consisting of water and air travels through a distance which is sufficient for complete dispersion of air (the jet velocity thus decreases by several times) to flow around a baffle. The baffle absorbs the jet energy and gives rise to secondary flows around the primary mixing zone in the backward direction, i.e. to the nozzle orifice. Owing to the provision of the baffle, the pulp first ascends, then moves horizontally and finally descends into a deaeration zone where aggregates in the form of a bubble and a particle are separated from the pulp flow. The size of the deaeration zone is 4-6 times greater than the primary zone size.
The disadvantage of the above described flotation machine resides in that the use of a turbulent submerged jet for breaking down air bubbles is not efficient enough so that fine air bubbles which are needed for the flotation of fine particles of mineral are not obtained.
At the same time, the velocity of the jet in flowing around the barrier is not sufficient for obtaining small-size bubbles.
The rather high velocity of flow in flowing around the baffle hampers complete separation of bubbles. A bubble which gets into the zone behind the baffle is subjected to the action of strong currents moving toward the outlet pipeline.
Known in the art is a flotation apparatus (German patent No. 1067743) having a cylindrical agitation chamber in which the height of a pulp column is 1.5-3.5 times the width of the chamber, and a pump which feeds the pulp being floated together with air to the agitation chamber. An auxiliary cone is installed at the top adjacent to the agitation chamber, the cone having a discharge opening for removing a part of the pulp overflowing therein from the agitation chamber.
A serious disadvantage of the above described flotation machine resides in a non-uniform distribution of air bubbles over the cross-section of the jet flowing through the agitation chamber.
As the jet has the maximum velocity at the axis, it is along the jet axis that the maximum yield of the material and bubble-particle aggregates takes place, hence, there is no zone of steady flow in the top part of the pulp column. In addition, the dispersion of air bubbles in the submerged turbulent ascendent jet is rather inefficient, and there are no small-size bubbles so that the possibility of flotation of fine particles is low.
It is an object of the invention to provide a method and a flotation machine for concentration ores of non-ferrous metals which make it possible to float large-size particles as well as normal-size particles in an efficient manner.
Another object of the invention is to improve the capacity in concentrating ores of non-ferrous metals by flotation.
A further object of the invention is to reduce power requirements for flotation.
Still another object of the invention is to provide a simple, small-size and inexpensive flotation machine.